Dose assessment of a neutron source handling system with a 241AmBe neutron source

Abstract

A neutron source handling system (NSHS) was fabricated to house the ²⁴¹AmBe neutron source that is used as an external neutron source for the subcritical reactor assembly of the Philippine Nuclear Research Institute (PNRI). The NSHS is a water-filled cylindrical stainless-steel container, where the water serves as the moderator and shielding for neutrons. OpenMC, an open-source radiation transport Monte Carlo code, is used to perform neutron and photon dose simulations. Dose distributions for the bare ²⁴¹AmBe neutron source were compared when the source is housed in the NSHS in plugged and unplugged configurations. Neutron dose decreased due to the attenuating effect of the water and HDPE plugs in the NSHS while photon doses increased due to the (n,γ) interaction of neutrons with the hydrogen content of the water and HDPE. Air phantoms located 50 cm and 100 cm away from the neutron source also confirm the decrease in neutron dose, by around 90%. Although a 300% increase was observed for photon dose, the total dose remain significantly lower than the dose limit in a single year for radiation workers. With only 9.0% and 0.9% of the dose limit calculated for the bare and unplugged NSHS source configurations, respectively. These demonstrate the effective shielding provided by the NSHS, which ensure the safety of researchers working with the ²⁴¹AmBe source.